/* package whatever; // don't place package name! */
import java.util.*;
import java.lang.*;
import java.io.*;
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
{
Scanner sc
= new Scanner
(System.
in);
float radio = sc.nextFloat();
double resultado = 3.14159 * (radio*radio);
System.
out.
print(resultado
+""); }
}
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